Grammy winner Taylor Swift has been tapped to host The Grammy Nominations Concert Live!!  Countdown to Music's Biggest Night.  The December 5 special on CBS, airing live from Nashville, will reveal the nominations in the top Grammy categories.  Taylor will co-host with LL Cool J. Maroon 5 has already been announced as a performer on the show; country star Luke Bryan will join them on the bill.  The show airs at 10 p.m. ET/PT on CBS.  Tickets for the event are available via Ticketmaster; if you go, you'll be treated to a one-hour exclusive concert following the live telecast.